Walking jack



J. F. JOY

WALKING JACK oct. 27, 1953 7 Sheets-Sheet l Filed June l5, 1949 7Sheets-Sheet 2 J. F. JOY

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Oct. 27, 1953 Filed June l5, 1949 J. F. JOY

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WALKING JACK Oct. 27, 1953 'r sheets-sheet 7 Filed June 15, 1949 kwa.

Patented Oct. 27, 1953 2,5'z,ozs

WALKING JACK Joseph F. Joy, Pittsbur Manufacturing Corn gh, Pa.,assignor to Joy pany, Pittsburgh, Pa., a

corporation of Pennsylvania Application June 15, 1949, Serial No. 99,292

10 Claims. (C1. 262--1) This invention relates to apparatus for mineroof control. y p

Rooi control is one of the most troublesome and expensive items inmining. This is so because of the expense oi the materials which have.`

customarily been used and because so large a percentage of the materialsemployed is lost as a result of roof subsidence as the Working faceadvances. The large amount of labor involved in building cribs, settingtimbers, etc., also adds.`

to the expense. Accordingly, if there be provided an effective rapidlyadjustable means for roof control-one that is relatively secure againstloss of its elements and which has a comparatively long lifeit will behighly desirable, and this:

will be so whether or not such devices be employed with long or shortfaces. In this application, I shall disclose, describe and claim animproved roof control arrangement which marks a substantial improvementover prior devices of` this character, in that there Will be not only aroof support by devices which may yield under increased roof pressurebut which shall further have the characteristic of being capable ofhaving their pressure upon the roof diminished during repositioningwithout the necessity for the release oi any fluid from them.

An object of my invention is to provide an improved and dependable meansresisting the closling of the gap caused in the strata of the earth bythe removal of certain layers thereof, such as coal seams or the like,such resistance being maintained for the full length of time to permitthe effective mining of such layers. An-

other objeet is to provide an improved roof supporting structure foryieldably sustaining the pressure of the roof and adapted to have thepressure exerted between the roof and the floor diminished whenadjustment or Walking of the roof supporting structure is to beaccomplished,

this without releasing any of the fluid medium4 with which the roofsupporting structure may have expansible chambers thereof lied. Stillanother object is to provide improved mechanically actuated structuresfor the control of mine;`

roofs which support the roof close up to the face along the roof line,but which have the jack devices ivhich. form a part thereof spaced farenough back from the face to permit efficient operation of coalproducing apparatus. object of my invention is to provide an improvedmethod of mine roof control. It is a further object to provide animproved roof jack mechanism. Another object is to provide an improved:roof jack mechanism which shall facilitate jack` Anetherv adjustment,through a temporary reduction in the force With which the mechanismengages the mine roof, but Without the dissipation of any part of theforce in such a manner that in the event of a sudden subsidence of theroof there would be an inadequate-reduced-force for sustaining the roofpressure. Still a further object of my invention is to provide animproved roof jack mechanism or the hydraulic type having incorporatedtherein means for providing for a limited degree of yield withoutventing of hydraulic iluid, and in which there may be an actualreduction in the pressure exerted by the jack mechanism on the roofWithout a corresponding reduction in the force which the jack mechanismis constantly ready to exert at any given elevation. Yet a furtherobject is to provide an improved roof control system having theadvantages of resilient yielding through the concurrent use of a trappedbody of gaseous fluid and a hydraulic iluid, together with the advantageof an over-riding control without the release of either the gaseous orhydraulic fluids. A further object of the invention is to provide an im-25 proved roof jack mechanism in which mechanical i the event of even aslight subsidence of the roof the full roof supporting pressure. Anotherobject is to provide an improved roof jack structure having an improvedroof engaging and supporting skid structure fully protecting underlyingworking parts. Still another object is to provide an improved jackmechanism including improved means for overcoming, Without releasing,the resilient pressure exerted on the roof during roof support. Stillanother object is to provide an improved roof jack mechanism having acombination of toggle mechanism and pressure fluid operated mechanismarranged between upper, roofand lower, Hoor-engaging elements, withimproved means for enabling the toggle mechanism to overcome the fluidoperated mechanism. Still a further object is to provide an improvedroof jack mechanism having improved means for adapting it to differentroof heights. Still another object of the invention is to provideimproved means for controlling the jacks of a. roof parture fromparallelism of its roof and floor purposes of illustration l have shownone embodiment which my invention may assume in practice,

Fig. l is a horizontal sectional view through a mine adjacent to alongwall working face, showing illustrative embodiments of the inventionfrom its apparatus aspect in use.

Fig. 2 is an enlarged sectional view on a Vertical plane correspondingto the plane of the section line 2-2 of Fig. l.

Fig. 3 is illustrative embodiment of my improved roof jack structure.

Fig. 4 is a side elevational view of the structure of Fig. 3.

Fig. 5 is a view corresponding to Fig. Ll, showing the roof supports atthe conclusion of one step of advance of the floor and roof engagingsupport elements.

Fig. 6 is a vertical transverse section on the plane of the line fi-t ofFig. 5, the parts being shown on a still larger scale.

Fig. 7 is a detail View, with parts broken away, showing one of thetoggle mechanisms, with provision for adjustment incorporated therein.

Fig. 8 section line 8-3 of Fig. 4, parts being shown on an enlargedscale and some parts being shown in full.

Fig. 9 is a further enlarged fragmentary sectional view on the plane ofthe section line 9-9 35 of Fig. 8.

Fig. l0 is a plan View on a considerably enlarged scale of a controlvalve mechanism.

Fig. 1l is a vertical section through the control valve mechanism ofFig. 10, the section being taken on the plane of the line II-II of Fig.10.

Fig. l2 is a vertical transverse section on the plane of the line IZ-i 2of Fig. ll.

Fig. 13 is an elevational View of the control valve mechanism of Fig.10, viewed from the 45 right-hand end thereof.

Fig. la is a fragmentary sectional view in the same plane as Fig. 11showing a distributing valve forming a portion of the valve mechanismmoved to a different position from the one shown 50 in Fig. 1l.

Fig. l5 is a partly diagrammatic View, with parts shown in section,illustrating the hydraulic system of the roof jack mechanism.

Referring now brieily, initially, to Fig. l, it will 65 be noted that alongitudinal face is indicated at l. This includes a portion IA whichhas been advanced one operation width X of a mining machine 2 beyond theportion IB which still remains to be mined out and advanced to aposition in line with the portion IA. The mining machine 2 may obviouslyassume various forms, and as shown has suitable mechanism 3 fordisintegrating the mineral, herein, coal. The vface I has at itsopposite ends spaces G and 5, and roadways 6 provided for ventilationand coal removal communicate with these spaces, which are really theends of the roadways. These roadways have been driven to the limits ofthe area to be mined out,

and are arranged between the ribs of a large .m unmined block of coal 'Iand side walls 8. The roof is indicated at e as having been caved'forthe full width of the distance between the side walls or ribs 3. Aconveyor I3 herein shown as a a further enlarged plan View of an 15 is ahorizontal section on the plane of forms, extends for the full width ofthe portion of the face which has been advanced, and its length isprogressively increased by one section each time the face is extended byan amount equal to the distance between the center lines of Ithe roofjack mechanism I which provide roof support between the face and thecaved portion of the roof. The conveyor I discharges onto a conveyorherein shown as a belt conveyor I2 which extends out through the roadwayB. The conveyor I0 may be driven by a suitable drive mechanism I3 ofconventional form and is made up of sections I4 of appropriate length,say, 8', new ones of which may be quickly attached to .the ends of theconveyor line as the disintegrating apparatus progresses along the face.Roof subsidence along the face is prevented by the improved roof jackmechanisms of this application, which are herein designated II as abovenoted, and these roof jack mechanisms by their construction and spacingare adapted to hold the roof from caving, except in the manner and tothe extent desired.

Now referring initially particularly to Figs. 3 and 4, it will beobserved that the apparatus shown includes an upper, roofload-sustaining support element 2l and spaced parallel mine bottomengaging support elements or skids 22, an anchor jack mechanism 23,front and rear roof load-sustaining jack structures 24 and 25, hereintwo of each, expansible chamber means 26 for effecting repositioning ofthe jack structures 24 and 25 relative to the anchor jack 23 and viceversa, and means generally designated 2I for at least partiallyrelieving the roof of the pressure of .the roof support 2| as adjustmentof the roof support relative to the anchor jack 23 is effected. The roofengaging structure 2l consists of a relatively wide plate structure 3Iconsiderably longer than its width and having a short downturned end 32,to make its advance smoother, and a considerably longer, more steep-lydownturned end or skid-like portion 33 at its rear end. This plateStructure is relatively rectangular in proj ection on a horizontalplane, save that there isa slot 35 formed in it at its rearward end ofsuitable width for the projection through it of the anchor jack 23 andof such length as to accommodate the relative movements between theanchor jack and the roof engaging member 2l. The plate 3i is stiifenedby laterally spaced members 36 extending for substantially the fulllength of the plate 3l and having secured to their lower edges plateelements 3l extending longitudinally beneath and in spaced relation tothe plate 3I and connected at 38 to the downwardly directed nose 32 andat 39 to the lower end of the most steeply downwardly directly skidlikeportion 33.

The lower support structure 22 includes H- beamlke members 4I as it werelying on their sides and having lower horizontal ilanges 42 providedwith upturned ends 43 and also provided with relatively horizontal upperflange portions 44 parallel to the portions 32. The members 4I are crossconnected to each other by cross shaft portions 45 and 43, and at theirfront ends the members 22 each carry a forwardly projecting bracket lil,each bracket rotatably supporting a guide roller48 for a shaker conveyortrough section 49. Rigidly secured to each of the spaced sideomembers ofthe iloor support base portion of the walking jack structure, adjacentthe opposite ends of each of the latter, are the jack devices shakerconveyor, but which may assume various 24 and 257 the former arrangednear the front end of the supports and the latter near the rear endsthereof. These jack devices include fixed cylinder elements 50 in whichtubular piston elements are reciprocable. Each piston element is of thetrunk type, as illustrated, and the piston elements of the jack devices24 each have a pivotal connection at 52 with a perforated ear 53 securedto the anges 3l at points approximately midway between the ends of theroof engaging support structure 2 I. The rearward jacks 25 simply havesuitably domed tops 55 engaging the surfaces of the flanges 3'| near`the downwardly inclined portions 39 thereof, as at 56. The pistons 5|are packed in any suitable manner (not shown) so as to prevent theescape of fluid around them from the bores of the cylinders 50.

The anchor jack 23 includes a vertical cylinder E0 mounted on a skid 6|shown as made up of channel irons 62 having their flanges extendinglongitudinally of the jack mechanism. The cylinder 60 has a piston 63reciprocable in it. This piston is a so-called trunk type piston also,and at its top engages an enlarged roof supporting plate E@ having aserrated top 65 adapted to be pressed into non-skid relation with themine roof. Upward movement of the piston 63 in the cylinder 60 causesthe anchor jack to provide a rigid abutment against which a thrust canbe exerted for the purpose of advancing the floor and roof engagingelements 22 and 2| and the several jack devices 24 and 25. On the otherhand, relief of pressure from the cylinder 50 will permit the anchorjack to be moved forward readily relative to the structure which hasbeen previously advanced with respect to it. The walking jack 26 issupported through the piston portion thereof on a clamping sleeve 'l0which is secured as at 1| about the upper end of the cylinder 60. Theclamping' sleeve carries a socket providing lug l2, in the socket 13 ofwhich the piston rod T4 of the walking jack piston 'l5 is fixedlysecured. The cylinder 'I6 of the walking jack receives the piston 'f5 inits bore and the cylinder 'I6 is reciprocable relative to the piston 15under the action of hydraulic fluid admitted to the opposite ends of thecylinder through conduits, respectively numbered i8 and T9, conduit 13leading Ito the rearward end of the cylinder 16 and the conduit "is toits forward end. The cylinder 16 has forward and rearward heads, as bestshown in Figs. 4, 5 and 8. The forward head 80 has projecting arms 8|between which a cross pin 82 extends, and the adjacent ends of togglelinks 83 and Se are connected to the pin 82. The end of link 83 is madein the form of a fork element which is connected by a screw 85 with atubular internally threaded element 86 carrying a sleeve ill iournaledon the cross shaft or bar 45. The

4end of link 34 is connected by a threaded element E33 with aninternally threaded tubular element $0 which is connected to a sleeve 9|which is iournaled on a forward cross shaft 92 extending between theiianges 36. The rear head of the walking jack cylinder has projectinglateral ears i0! in which adjusting screws |02 are arranged. These areadapted to engage head elements |03 connected by threaded rods |015 totubular internally threaded elements |05 which are pivotally supportedon the cross shaft or bar 4S. The members H23 are each connected bycross pins i H5 to forked end members which are connested by threadedelements H2 with internally threaded elements H3, and the two internallythreaded elements 3 are connected at their upper ends by collars ||4 toa cross shaft l|5 `extending between the flanges 36 at a pointadjustability and nearer the rear ends thereof. By having the cross pin82 directly fastened to the cylinder head B0 but having adjustment ofthe effective length of the adjusting screws |02 a possibility, it willbe appreciated that absolute parallelism of the roof engaging member 2|and of the floor engaging member 22 is not requisite, and that if theadjusting screws |02 are screwed outwardly in their supporting ears,that is, to the left i'n Fig. 8, there may be a somewhat greaterdistance between the most remote surfaces of the door and roof engagingmembers at points in line with the axes of the yjacks 25 than existsbetween points in these members in line with the axes of the jacks 24.C'orrespondingly, by turning the screws |02 further forwardly throughtheir supporting ears, there may be a convergence of the top and bottomsurfaces of the jack mechanism toward the rear. Normally, however, whenthe arms of the toggle mechanism are parallel to each other the screws|02 will be slightly out of contact with the end members |03, with theresult that, as the walking jack cylinder l5 moves forwardly in a mannerhereinafter described, the pressure applied by the roof jack elements 24will be diminished somewhat before the pressure exerted by the roofjacks 25 commences to be overcome.

Before describing the system in more detail, the modification of atoggle mechanism shown in Fig. 7 may be noted. Here it will be notedthat a hand wheel controlled turnbuckle 6 is arranged between the headelement |03 and pivot members Ill rotatably supported by the cross shaftA6, and a hand wheel controlled turnbuckle I8 is arranged between theforked end members Ill' and the collars H4 mounted on the cross shaftH5. Similar arrangements may be provided for the other rear toggledevice, or for al1 of the toggle devices, thus providing for greatergreater relative adjustability between the elements 2| and 22.

The system for the operation of the several jacks mentioned can best beunderstood by refi storage tank |20 through a conduit |2|.

or it could be used for erence to Figs. 8, 9 and 15, `and a principalcon` trolling valve structure forming a portion of the system is shownin the several figures numbered l0, ll, l2, i3 and le. The fluid for theextension of the several roof jacks and of the anchor jack and for theeffecting of relative extension and collapse of the walking `jack issupplied from the This conduit |2| communicates with a connection |23 inwhich a hand operated pump |24 having a built-in relief valve isprovided. It will be appreciated that the hand pump |24, which is of awellknown commercial type, may be used vto effect the pumping of fluidfrom the storage tank |20, pumping fluid back into the storage tank |20.The hand pump has a conduit |25 at its opposite side from the conduit|23, and this conduit enters a valve block |26 at |21, and communicateswith a port |28 therein. The port |28 extends into a larger passage |29,shown in Figs. 11, l2 and 14 as extending vertically. There alsocommunicates with the passage |29 a passage |30, this being in line withthe passage |28, as illustrated, and having in communication with it aconduit |3| which constitutes a discharge connection from a motor drivenpump |32 whose driving motor |33 may be mounted in any suitable positionon the apparatus, as, for ex ample, on one of the door-engagingstructures 22. This pump too will have a built-in adjustable reliefvalve (not shown). The suction line |34 el! ltl'iepump 132 Vopens into agenerally U-shaped passage 135 extending transversely of the valvevblock 126 near the top of the latter, and a conduit 131, alsocommunicating with the cross passage 135, is connected with the tankthrough the conduit 121. At the lower end of the vertical passage 129,previously mentioned, there is provided a transversely lextendingpassage 140 surrounded by a valve seat 141 on which valve seat vamanually adjustable valve 142 having a controlling hand wheel 143 isadapted to seat. When the valve 1-42 is opened, rluid may pass freelybetween the passage 129 and a conduit 144 which is connected by a branchconduit 145 with one of the rear jacks 25, and through Va branch conduit146 with another conduit 141 leading to one of the front jacks 24, andthrough Aa conduit 148 and branch conduits 149 and 150 respectively, tothe other of the rear jacks 25 and to the other of the front jacks 24.The conduits 18 and 19 open into the valve block 126, and 'are adapted,upon opening movement of valve members 152 and 153, which respectivelyhave hand wheels 154 and 155, to communicate with passages 156 and 151which open into annular grooves 158 and 159 which are arranged at theopposite sides of an annular groove 150 with which the passage 129communicates and from Vwhich another passage 151 in line with thepassage 129 opens out. A valve 162 having a controlling hand wheel 163controls the communication of the passage 161 with a conduit 164, whichlast conduit communicates with a tube 165 extending through the cylinder16, and a bore 156 inthe piston 15 and the piston rod '14, and the bore166 is in communication with a conduit 151 opening into the bottom ofthe anchor jack Two other annular grooves 111 and 112 are arrangedco-axially with the grooves 153, 159 and 160 and respectively at thesides more remote from the groove 160 of the grooves 159 and 150. Thegrooves 111 and 112 communicate respec- -tively with the passages or armportions 113 and v114 of the transverse passage 135. Above the passage161 and the valve 162 there is a further extension of the passage 161,this extension being numbered 111 and being surrounded by valve seatv118 on which a valve 1.19 is adapted to seat. The valve 119 has a stem100 with which an O-ring seal 181 cooperates, and has a pivoted controllever 1182 having one end pivoted at 183 by means of ears 184 cn thevalve block 126 and a cross pin 185, and having an operating handle H atits opposite end.

The several grooves 158, 159, 160, 111 and 112 surround aperforatedsleeve element S containing a valve receiving bore 186 in which atwospool piston valve 181 is reciprocable. The valve sleeve is traversedby five circumferentially arranged sets of ports, each set arranged inone of the annular grooves. The ports of these sets are numbered:

With respect to the groove |58: 188 With respect to the groove 159: 189

'With respect to the groove 160: 1 90 With respect to the groove 111:191,'and With respect to the groove 1121192.

The spools 193 and 194 of the valve member are Vspaced by an annulargroove 195 whose length is .in lthe oppositely disposed end positions ofthe valvemember 1181, When the valve is pushed in one direction from thecentralposition shown in Fig. ll, to the right in that figure, thepassage 1.29: is connected with the passage 151 and the pas-- sage 1515is connected with the passage 114. In theoppositely disposed position ofthe valve y181, the passage 129 is connected with the passage 156,.while the passage 151 is connected with the passage 113. The valve hasenlarged end portions 195 and 191. These, in the central position of thevalve, are adapted to be simultaneously con-- tacted, or at least almostcontacted, by tubular follower thimbles 193 and 199 which are spring--pressed toward shoulders 200 and 201 in enlarged bores 202 and 203 inthe valve sleeve S. Springs 204 and 205 are provided to press thethimbles toward their shoulders and to center the valve 181 normally.Suitable packings 206 and 201 are arranged outside the springs tocooperate with extension stems 208 and 209 on the valve 181. The stem208 has an operating lever 210 having a grasping portion 21 1 and apivotal support at one end 212.

It will be evident that, whether iiuid be supplied from the tank by thehand operated pump through the passage 128 or by the motor operated pump132 through the passage 130, the fluid so supplied will pass freelythrough the passage 129, the annular groove 160, the passage 161, aroundthe stem of the valve 162, through the passage 111, past the valve 119,if this be open, through the passage 135, the connection 131 and theconduit 121 back to the tank 120. In other words, there will simply be,Whenever the valve 11s is open, a circulation of fluid Without thedevelopment of any substantial pressure. When the lever H is used topress the valve 119 onto the seat 118, this free return of fluid will beprevented, and a pressure will build up within the passage 129, theannular groove and the passage 161 which will be determined by thesetting of the relief valve associated with Whichever one of the pumps124 or 132 is the source of the pressure. Of course, separate externalconnections, each with a suitable relief valve, could be connectedbetween the conduits 123 and 125 and the conduits 131 and 134. So longas all of the valves 142, 152, 153 and 162 are closed and the valve 181is in the central position thereof shown in Fig. ll, no fluid will bedelivered to any of the operating devices. If the valve 142 is opened,however, fluid will be delivered to the roof jacks 24 and 25 through theconduits 144, 145, 145, 141, 143, 149 and 150. The pressure which willbe built up within these roof jacks will be determined by the reliefvalves mentioned, but, as shown in Fig. 8, an accumulator is arranged incommunication with the conduit 149 through a conduit 215. Thisaccumulator is of a well known construction, and includes a metallicwalled chamber 216 in which there is arranged a collapsible Huid-tightbag 211 carrying a valve element 218 on the end thereof towards thepoint of communication of the conduit 215 with the casing 216. It willbe noted in Fig. 8 that an annular valve seat 210 surrounds the passage220 through which the conduit 215 communicates with the interior of thecasing 215. The collapsible bag 211 will be prefilled with a gaseousfluid under a considerable pressure on the order of a number of hundredsof pounds per square inch, and nitrogen may conveniently be used as thisgaseous uid. This accumulator provides for .the maintenance of ayielding pressure by the hydraulic jacks 24 and 25 forcing the roofengaging plate structure 21 and the base structure 22 apart andmaintaining a desired pressure on the roof. This may be on the order of371/2 tons per jack for a roof support 2| on the order of 20 long and 6wide.

Reverting to the conditions when the valve |42 is open, it will be notedthat iiuid will be supplied to the jacks 24 and 25 if the Valve |19 isclosed, but will drain back out of the jacks if the valve Vis is open.Fluid may be admitted to the anchor jack 23 by opening the valve |62 andclosing the valve |19. Because the accumulator 2|6 will havecommunication with the anchor jack 23 through the conduits 2|5, |49,|48, |46 and |44 and passages |29, groove |60, passage |6|, conduit |64,tube 65 and conduits |66 and |61, the anchor jack may also exert ayielding pressure on the roof so long as the valve |42 is open. If theoperator releases the handle H, however, all the iluid supplied to thesejacks will commence to escape, and accordingly, the valves i42 and |62will normally be closed when such pressure has been built up in thejacks which they respectively control, as may be desired. By opening thevalves |2 and |53, it will be possible respectively to advance theanchor jack relative to the roof jacks and to advance the roof jacks andthe upper and lower support devices 2| and 22 relative to the anchorjack. Ordinarily, there will be no occasion for maintaining pressure onthe anchor jack except when it is desired to move the roof jacksforwardly, but if it is desired to provide the cumulative pressures ofthe roof jacks and the anchor jack on the mine roof, this is possiblethrough proper control of the various valves.

When it is desired to advance the roof load sustaining support 2l andthe mine bottom engaging skids 22, normally fluid will be entrapped ineach of the four roof jacks and in the anchor jack. Each of the fivejacks will exert a force on the order of 371/2 tons with theconstruction and in an apparatus of the size mentioned, or, a total of1871/2 tons. To this could be added, it may be noted in passing, afurther large amount of pressure if the toggle devices which can haveforce exerted through them by the horizontal jack cylinder have thelatter employed to tend to straighten them. It Will be clear that withthe four roof jacks cumulatively exerting 150 tons pressure on the mineroof, the anchor jack, with but 371/2 tons of roof pressure, wouldperhaps slip first, notwithstanding its special serrated roof surfaceengaging construction, if the action of iiuid admitted between thepiston 'l5 and the cylinder head 8|] simply exerted oppositelongitudinal thrusts on the anchor jack and on the skid and roof supportforced apart by the roof jacks. However, the frictional resistance tosliding the skids and roof support plate is much less than that of thebase and top of the anchor jack, and the mechanical advantage with thetoggle connections shown is very great, and the forward thrust of thewalking cylinder first greatly reduces the `pressure exerted by thejacks 24 on the roof, and then, as the screws |02 engage the elements|03, also the pressure exerted by the jacks 25, and as the hydraulicallyapplied pressures maintained by the action of the accumulator (whosepresence permits any slight displacement of liquid desirable tofacilitate advance of the roof support) is greatly offset by the forcestransmitted through the toggles, there is an advance of the roof supportas desired. It may be noted that if the roof should suddenly lowerenough to tend to collapse the roof jacks beyond the points to which thetoggles might have brought them the full force of the jacks would beinstantly available to sustain the roof, assuming there was not acontinued admission of liquid to the walking jack in such manner as tocause the toggles to reexert their counter force. Release cf the handleI-I would in any event instantly make the full roof supporting forceavailable.

The general mode of operation is clear from what has already beenexplained, but it may be noted that as rapidly as the mining apparatusmoves beyond the line of advance of a unit, the latter will be advanceduntil its end 32 is closely adjacent the newly formed face, and the iullpressures of both the roof jacks 24 and 25 and of the anchor jack 23 maybe made use of in supporting the roof. The iront toggle mechanism evencan be used, by admitting fluid to eifect a retracting force on thecylinder of the walking jack 26, to augment the roof supportingpressure. The shaker pan section of each unit will be connected to thepan line as soon as the section has been moved into line with thepreviously connected and operating pan line.

The apparatus of the invention is strong, is very readily controlled,does not require a potentially dangerous relief of roof supportingpressure for its advance, and has a control system which, by the closureof the lines to the energized roof and anchor jacks, produces acondition in which the mere release of the handle H will result in aninstantaneous reapplication of the full roof supporting pressure.

While there is in this application specically disclosed one form, and amodification thereof, which the invention may assume in practice, itwill be understood that these are shown for purposes of illustration andthat the invention may be further modified and embodied in various otherforms without departing from its spirit or the scope of the appendedclaims.

What I claim as new and desire to secure by Letters Patent is:

l. In combination, a mine oor engaging support, a mine roof engagingframe, forwardly and rearwardly disposed jack devices yieldinglypressing said support and frame apart and causing said frame to exert ayielding supporting pressure on the roof, traction elements extending'between said support and frame and connected at their opposite endsrespectively to said support and frame, an abutment jack, and feedingmeans reacting upon said abutment jack and acting upon said tractionelements at points intermediate their connections to said frame and saidsupport for forcing said points, in the direction of feed, away from astraight line extending through the connections of said elements withsaid frame and support, to cause the exertion of a traction towards eachother between said frame and support and of a longitudinal feeding forceupon ,both of them.

2. In a roof control apparatus, mine floor engaging supporting means,mine roof engaging and supporting means, jack means extending betweensaid mine floor engaging supporting means and said mine roof engagingand supporting means, said jack means including means for yieldinglypressing said first two means apart, anchor jack means engageable withthe mine anchor jack means engageable with the mine floor and mine roof,walking jack means connected at one end with said anchor jack means, andan operative connection between said walking jack flflY Y means andsaid.mine iioor engaging supporting means and said mine roof engaging andsupporting `means including devices connected to said rst two meansforcausing a major component of the force exerted 'by said walking jackmeans to Vbe transitted to said nrst two means in such a di-- rection asto subtract from the separative forces exerted by said first mentionedjack means, said operative connection including elements having theiropposite ends connected for relative movement; as said supporting meansundergo relative movement and engaged `between their ends by saidwalking jack means in such a direction that extension of said walkingjack means tends to cause AVa vreduction in distance between saidopposite ends. n

3. Ina roof control apparatus, mine floor enfgaging supporting means,mine root `engaging andvsupporting means, jack means extending be--tween said `mine floor engaging supportingmeans and said mine roofengaging and supporting means, said jack lmeans including Ameans foryieldingly pressing said rst 4twoumea'ns apart, anchor jack meansengageable with the mine floor and mine roof, vrwalking vjack means"connected at one end with said Aanchor jack means, and lan Yoperativeconnection'between said walk ing jack means and Vsaidinine floor'engaging supporting meansand said mine roof engaging and supportingmeans including means for causing a major component of the force exertedby said walking jack means to be transmitted to said first two means insuch a direction as at least to `tend to cause approach of vthe second'to the first while said first 'mentioned jack means are acting to pressthem apart, said last recited means including toggle devices havingupp'er and lower ends connected respectively to said mine roof engagingand supporting means and to said mine idoor engaging supporting meansand having their central portions pressed b'y 'said walking `jack means,as the latter is extended, in a direction to effect mutual approach of'their ends. l

4, In a .roof control apparatus, 'mine floor engaging supporting means,mine roof engaging and supporting means, jack means extending betweensaid mine floor engaging supporting means and said mine roof engagingand supporting means, Vsaid jack means including 'forwardly andrearwardly disposed ljack devices for yieldingly pressing said first twomeans apart, anchor 'jack means engageable with the mine floor and mineroof, walking jack means connected at 'one end with said anchor jackmeans, and an operative connection between said walking jack means Vandsaid rst two means including forwardly and rearwardly disposed toggledevices connected with said first two means 4'for causing a majorcomponent of the force exerted by said walking jack means tobetransmitted to said first two means in a directionto cause approach ofthe second to the iirst.

'5. 'In a roof control apparatus, mine door engaging supporting means,mine roof engaging and supportingmeans, jack means, respectivelyadjacent the forward and rearward ends of said floor engaging means,extending between said mine iioor engaging supporting means and saidm-ine roof engaging and supporting means, said jack means includingmeans for yieldingly pressingsaidirst two means apart, anchor jack meansengageable with the mine floor and mine roof, walking jack meansconnected rat one end with said anchoi` jack means, and an operativecon- 12 nectionfbetween lsaid walking jack fm said mine roof Mengaging vand supporting means and said mine fioo'r engaging supporting meansincluding toggle means, respectively adjacent the forward endandadjacent the center of saidffloor engaging supporting means, andmeans forwren-- dering said toggle Vmeans sequentially effective forcausing, a maior Component of the force 'x- -erted`by Vsaid 'walkingYjack means to be 'trans- -V -ter wherein there is provided roofSupporting means including mine ioor engaging supporting means and mineroof engaging and supporting means and jack means, including a forwardjack and a rearward jack at either side, yield'ably forcing apart Vthemine floor engaging supporting means and the'inine roof engagingandisu'pporting means, and wherein there is provided'an abutmentjack'expansible into vfirm vcontact with the floor and roof, 'and inwhich 'there is further provided a cylinder and piston 'mechanismVconnected 'at one end to said abutment jack vand operatively connected'at its other end with 'said roof engaging and supporting means and 'oorengaging supporting means and which is 'selec'- tively operable toadvance said abutment jack,

` 0r, When vSaid abutil'ent jack iS in 'flll Contact with the iioor androof, lto advance said roof supporting mea'ri's,'the arrangement in'which said operative connections. include toggle 1links'piv'-V otallyconnected together and `at their mutually opposite ends pivotallyconnected with said mine door engaging supporting means and said mineroof engaging and supporting means 'and said cylinder and pistonmechanism acts on -said togggle links in a direction to decrease theincluded angle between said links upon extension-of said cylinder and'piston mechanism in the direction of feed. y

'7. In a roof control apparatus of the character wherein roof supportingmeans is provided including mine floor engaging supporting means andmineroof engaging and supporting means and four jack means yieldably forcingVapart the mine iioor engaging supporting means 'and the mine roofengaging and supporting means, and in which an abutment jack is providedwhich is at will expansible into firm contact with the floor and roof,and there is `provided a cylinder and piston mechanism connected at oneend to said abutment jack and operatively Vconnected 'at its other endwith said roof supporting means V'and which is selectively `operable toadvance 'said abutment jack, or, when said abutment jack `is in 'firmYcontact with the floor vand roof, to advance said roof supportingmeans, the provision of toggle connections lpivotally connected to saidmine oo'r engaging supporting means and 'to vsaid mine roof engaging andsupporting means and engaged by said cylinder and piston mechanism` andtransmitting longitudinal thrust to said rot'f supporting means and,when the thrust necessary to advance said roof supporting means exceedsa predetermined value, reducing the Veffective pressure which said 'fourjack means cause 'to be exerted on the mine roof and floor. Y

8. In a roof control apparatus of the character wherein roof supportingmeans isprovided including mine floor engaging supporting vmeans andmine roof engaging and supporting means and jack means, which jack meansyieldably force apart the mine floor and mine roof engageans vand ingsupporting means, and in which an abutment jack is provided which is atwill expansible into rm contact with the oor and roof, and there isprovided a cylinder and piston mechanism connected at one end to saidabutment jack and operatively connected at its other end with said roofsupporting means and which is selectively operable to advance saidabutment jack, or, when said abutment jack is in rm contact with thefloor and roof, to advance said roof supporting means, the provision ofoperative connections between said cylinder and piston mechanism andsaid roof supporting means which not only transmit longitudinal thrustto the latter, but are operative when the thrust necessary to advancesaid roof supporting means exceeds a predetermined value to reduce theeffective pressure which said jack means cause to be exerted on the mineroof and floor, said operative connections including toggle mechanismsspaced apart longitudinally of said apparatus and connected between themine floor engaging supporting means and said mine roof engaging andsupporting means and each having its joint engaged by said cylinder andpiston mechanism and arranged to be collapsed on the extension of thelatter.

9. In a mobile roof jack mechanism for mines, a base engageable with afloor surface, a roof engaging top overlying said base, power operateddevices operatively connected to said base and said top for yieldinglyforcing the same apart into roof supporting relation, an anchor deviceengageable with extraneous means, a horizontal feeding deviceoperatively connected to said anchor device for moving said base and tophorizontally relative to the floor and roof, and an operative connectionbetween said feeding device and said base and top including means forcausing a major component of the force exerted by said feeding device tobe transmitted to said base and top in a direction to reduce the forcewhich urges said base and said top apart, said operative connectionincluding devices having opposite ends moved apart upon separativemovement between said base and top, and connected between their endswith said feeding device and pressed by said feeding device in adirection to form a decreasing angle between their opposite end portionsas feeding takes place.

10. In a portable mine roof jack, a base adapted to rest on the oor of amine, roof engaging and supporting means for engaging and supporting themine roof, power operated devices operatively connected between saidbase and said roof engaging and supporting means for yieldingly forcingsaid roof engaging and supporting means upwardly into roof supportingposition re1- ative to said base, an anchor device engageable withextraneous means, toggle devices operatively connected between said baseand said roof engaging and supporting means, and a horizontal feedingdevice operatively connected to said anchor device and to said toggledevices: for moving said base and said roof engaging and supportingmeans horizontally relative to the floor and roof, said feeding deviceacting on said toggle devices in a direction to decrease the includedangles of said toggle devices whereby, when a predetermined feedingforce is applied to said toggle devices, they reduce the force whichserves to press said roof engaging and supporting means against theroof.

JOSEPH F. JOY.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 1,116,357 Morgan Nov. 3, 1914 1,480,733 Morgan Jan. 15, 19241,481,875 Morgan Jan. 29, 1924 1,639,050 Morgan Aug. 16, 1927 1,704,866Morgan Mar. 12, 1929

